Universal joint for driving impact wrench sockets



Dec. 12, 1961 R. J. SCHAEDLER 3,012,420

UNIVERSAL JOINT FOR DRIVING IMPACT WRENCH SOCKETS Filed May 15. 1960 United States Patent Ofitice 3,012,420 Patented Dec. 12, 1961 3,012,420 UNIVERSAL JOINT FOR DRIVING IMPACT WRENCH SOCKETS Raymond J. Schaedler, Utica, N.Y., assignor to Chicago Pneumatic Tool Company, New York, N.Y., a corporation of New Jersey Filed May 13, 1960, Ser. No. 29,096 11 Claims. (Cl. 64-7) This invention relates to universal joints adapted to transmit torque from a power operated wrench to a wrench socket disposed on an axis oblique to that of the wrench. The invention has especial, although not exclusive, application to impact wrenches.

The usual irnpact wrench comprises a tool head having a square or splined front end adapted to fit directly into the rear end of a wrench socket, which, in turn, fits over the head of the bolt or nut being driven. The tool head is formed as an integral extension of an anvil and transmits rotational impacts through the wrench socket to the driven nut. When operating in close quarters it is sometimes necessary to hold the wrench with the axis of the tool head extending obliquely tothe axis of the wrench socket, in which case a universal joint is employed. The usual universal joint comprises a socket member detachably connected to the tool head, a shaft member detachably connected to the wrench socket, the rear end of the shaft member having a knob supported forsuniversal movement within the front end of the socket member, and a cross rod or drive pin extending transversely of the knob and arranged to transmit torsional impulses from the socket member. The conventional drive pin is in the shape of a thin cylinder having tangential contact with the sides of a diametrical slot in the knob portion of the shaft member. This pin serves to transmit the entire force of the torsional impact along the line of tangency with the side wall of the slot, and theconcentration of a large force over a very minute area causes the pin to wear very rapidly particularly near the outer end of the knob. As the pin wears, the connection becomes loose and part of the force of the torsional impact is dissipated in accelerating the heavy socket member during the period in which it takes up the lost motion caused by the worn pin. The lost motion also causes the pin to hammer against the side walls of the knob portion of the shaft thus increasing the wear and eventually causing fatigue failure and breakage of the pin.

Anobject of this invention is to prevent excessive wear and breakage of the drive pin connecting the socket memher with the shaft member. in accordance with this invention, the drive pin is formed with a square cross section having two flat sides fitting the side walls of the slot in the knob. The change in shape of the pin gives it greater strength because it makes possible a larger area of cross section for the same width of slot. It also spreads the force of the torsional impulse over a relatively wide area instead of concentrating it on a single line of contact as in the prior art.

Another object of this invention is the provision of a universal joint which can be quickly assembled and disassembled when it is desired to replace any part. In accordance with this invention the driving pin is supported within trunnions which are mounted for rotation in radial bores in the socket member. A novel form of retainer means is provided for holding the trunnions and the through registering bores in the socket member. With this arrangement, all of the parts of the retaining means are enclosed within the periphery of the socket member. Furthermore, there is no need for any swaging or riveting operation at the ends of the drive pin.

Another object of the invention is to simplify the construction and reduce the manufacturing cost of a universal joint. In accordance with this invention, the recess at the front end of the socket member, which is adapted to receive the knob, is formed as a cylindrical surface which can be machined easily. The cylindrical recess permits the knob to be inserted and removed conveniently when the retainer pin is disassembled. However, the invention provides means for preventing the removal of the knob from the socket member when the retainer pin and trunnions are in assembled relation to the socket member.

A feature of the invention resides in the shape of the diametrical slot in the knob. The slot is closed at its rear end thus cooperating with the drive pin to retain the knob against separation from the socket member. The closed end of the slot also prevents the sides of the slot from spreading and possibly causing fatigue failure under the strain of torsional impacts. In longitudinal section, the diametrical slot consists of two sectors, each having end walls extending in a generally radial direction. Each end wall is in the shape of a half cylinder arranged tangentially to the flat side walls of the slot. This particular shape facilitates manufacture and also aids in preventing fatigue failure by eliminating any sharp corners.

Another feature of the invention resides in the shape of the trunnions, each of which has a spherical zone fitting a complementary shaped portion of the surface of the knob. The trunnions, therefore, frictionally engage the knob and tend to resist relative movement between the knob and the socket member which supports the trunnions.

Other objects and features of the invention will appear more clearly from the following description, taken in connection with the accompanying drawings and appended claims.

In the accompanying drawings which shows one form of the invention:

FIG. 1 is a longitudinal section of a universal joint embodying this invention;

FIG. 2 is a cross-section along the line 22 of FIG. 1 looking rearwardly, with part of the shaft knob broken away; I

FIG. 3 is a fragmentary section along the line 3--3 of FIG. 1 looking downwardly;

FIG. 4 is an enlarged view of one of the trunnions in longitudinal section;

FIG. 5 is an enlarged cross-section through the driving pin and trunnion along the line 55 of FIG. 2 looking downwardly;

FIG. 6 is an enlarged sectional view of the drive pin and of the surrounding portions of the knob, along the irregular line 66 of FIG. 1, loking downwardly; and

FIG. 7 is a further enlarged end view of the retainer pm.

Referring to FIG. 1, the illustrative joint comprises a socket member 10, a shaft member 11 connected thereto for relative universal movement, a drive pin 12 for imparting torque from the socket member to the shaft memher, and a pair of trunnions 13 for swivelly supporting the drive pin in the socket member. The rear part of the socket member includes an annular wall 14 which surrounds a central opening 15. The rear portion of the opening is surrounded by a series of splines 16 extending inwardly from the wall 14. The splines are arranged to engage a complementary splined anvil (not shown) at the front end of an impact wrench (not shown), and the splines serve to transmit a rotative drive and also torsional impacts from the anvil to the socket member 10. Forwardly of the splined portion, the openinglS is cylindrical and has a diameter which extends slightly beyond the depth of the grooves 18 between the splines 16. Access to the central opening is provided by an oblique slot 19 (FIGS. 1 and 3) which extends from the opening 15 in an outward and forward direction through the annular wall 14. For a further description of the structure and function of the slot 19 and splines 16, reference is made to patent application Serial Number 704,467, new iatent No. 2,954,994, filed December 23, 1957 by Robert T. Beers on a socket retainer for rotary power tools.

Forwardly of the annular wall 14, the socket member 7 10 has a head portion 21. As shown best in FIG. 3, the

head portion has a short cylindrical'bore 22 adjacent the opening 15, a relatively long cylindrical recess or counterbore 23 spaced forwardly of the short bore, and a chamfered'surface 24 extending from the front end of the counterbore to the front extremity of'the socket member 10. The short bore and the long counterbore are connected by a shoulder 25. The surface of the shoulder 25 has the shape of a frustum of a cone whose axis coincides with the axis of the chamfered surface 24, bores 22 and 23 and opening 15.

Shaft member 11 has a splined portion 27, a short cylindrical stem portion 28 and a knob 29. The splined portion is arranged to engage a wrench socket member (not shown) of the type shown in the Robert T. Beers patent application aforesaid. Alternatively, the splined portion 27 may have driving engagement with another universal joint like the joint shown in FIG. 1, in which case the splines and grooves on the shaft member 11 would interfit with the grooves 18 and splines 16 respectively in the socket member 10. The knob has a cylindrical surface ofsuch diameter that it has tangential con- A by the operator as he pushes the entire machine toward the nut or bolt (not shown) being driven.

In order to transmit torque in the form of torsional impulses or impacts from the socket member 10 to the shaft member 11, at any selected angular relation, a novel form of pin and slot connection is provided. The connection comprises a slot 31 extending diametrically from the top to the bottom of the knob 29. The slot has vertical walls which have sliding contact with the drive pin 12. When the drive pin is supported in the vertical position shown in 1, it guides the shaft member 11 for tilting movement between the extreme supper position in which the shaft lies along the axis 32 and the extreme lower position in which the shaft lies along the axis 33. Tilting movement is limited by engagement between the stem portion 28 and the chamfered surface 24 on the socket member 10. The diametrical slot 31 comprises an upper segment and a lower segment, each having suflicient arcuate length to permit tilting between the limits 32 and 33 aforesaid without interference with the drive pin 12. The upper and lower segments of slots 31 are separated by a solid wall 34 at the rear end of the knob 29. The wall 34 serves as a retainer to prevent the shaft 11 from being pulled out of the socket member 10 as long as the drive pin 32 is attached to the socket member. The end wall 34 also serves another purpose in preventing fatigue failure and breakage as will be described later. The wall 34 is integral with the remaining parts of the shaft member 11 including the splined portion 27.

. According to a feature of this invention, the drive pin 12 is substantially square in cross section, with chamfered corners 35 (in FIG. 6), and the upper and lower ends. of the pin are supported in openings 36 of complementary shape in the trunnions 13, as shown in FIGS. 4 and 5.

Each trunnion has a cylindrical periphery supported for swivel movement in a vertical bore 37 in the head portion 21'of the socket member 10. Each trunnion has a concave face 38 adapted for frictional engagement with the portion of the knob 29 which lies adjacent the diametrical slot 31. With this arrangement, the shaft member 11 may be tilted without moving the drive pin 12 or trunnions 13 or socket member 10, in which case the concave faces 38 guide the shaft member 11 for tilting movement about an horizontal axis passing through the center of the knob. Alternatively, the shaft member 11 may be swung horizontally in which case the shaft member 11, drive pin 12 and trunnions 13 all swing or turn in unison relative to the socket member 10, and the trunnions 13 guide the shaft member for swinging about the vertical axis of the trunnions and surrounding bores 37. It will be understood' that the shaft member may be moved universally relative to the socket member 10, that is moved with a horizontal swing component of motion and a vertical tilting component of motion at the same time. The trunnions 13 do not move relative to the drive pin 12, but the trunnions and pin may move together as a unit either about a vertical axis relative to socket member 10, or about a horizontal axis relative to shaft member 11, or both at the same time.

In order to maintain the trunnions 13 in frictional engagement with the knob 29, each trunnion is provided with a diametrical bore 39 (FIGS. 4 and 5) which registers with a diametrical bore 41 in the drive pin 12. A retainer pin 42 is snugly received within bore 41 of the drive pin; a

As shown in FIG. 7, the retainer pin is of the spiral roll type consisting of a fiat strip of metal rolled into a substantially cylindrical shape and having a normal diameter, when disassembled, which is slightly greater than that of the bore 41. At each end the retainer pin has a chamfer 43 which permits the pin to be forced into the bore 41 by hammering on the other end of the pin. When assembled, the retainer pin exerts a reactive force outward against the bore 41 thereby holding the retainer pin in snug frictional engagement with the drive pin 12. This engagement is so tight that no other means need be provided for preventing accidental displacement of the retainer pin with respect to the drive pin during. the normal operation of the universal joint in connection with an impact wrench. The retainer pin 42 has a length greater than the width of the drive pin 12 but less than the diameter of the trunnions 13.

In accordance with a feature of this invention the trunnion bores 39 are made slightly larger in diameter than the drive pin bore 41thereby leaving clearance space around the end portions of the retainer pin. Thisclearance space facilitates assembly and disassembly of the retainer pin by confining the frictional grip to the middle portion of the retainer pin and also by avoiding any bending or peening action action on the ends of the retainer pin, 'such as might otherwise occur upon relative movement of the drive pin 12 about the axis of the trunnions 13 during the transmission of impacts. The diametrical bore 39 in the trunnions registers with a pair of bores 44 in the head portion 21 of the socket member 10, the bores 44 preferably having the same diameter as the trunnion bores 39. There is one bore 44 on each side of the upper trunnion 13, thereby permitting the insertion of a hammer pin for the assembly and disassembly of the retainer pin.

In use, the operator inserts the splined portion 27 of the shaft 11 into a Wrench socket and slips the splined portion 16 of the socket member 19 over the projecting wall 14, head portion 21, trunnions 13, drive pin 12, knob 29 and then through the shaft splines 27 to the wrench socket member (not shown), through the flexible driving connection just described. There is very little lost motion, and therefore, the hammer blows on the anvil are not materially attenuated by accelerating any part to take up the lost motion. The force of the rotary impacts delivered by the drive pin 12 to the knob 29 has a tendency to shear the drive pin as usual. However, this tendency is efiectively resisted during the operation of the present invention because the fiat sides of the drive pin 12 have surface contact with the flat walls of the slot 31 over a very large area, whereas in prior constructions employing cylindrical drive pins, the pin engaged the slot with line contact, and the concentration of the torsional impact over a minute area of the pin produced a rapid wear and often fatigue failure and breakage of the pin. Another reason that the drive pin 12 is less likely to break than the usual cylindrical pin is that it has a larger cross sectional area for the same width of slot 31.

The torsional impacts delivered to the drive pin 12 and to the knob 29 have the usual tendency to spread the knob apart on opposite sides of the diametrical slot 31 which might eventually cause fatigue failure at the front end of the slot. However, fatigue failure is effectively prevented by this invention because the solid wall 34 closes the rear end of the slot 31 to prevent spreading at the sides of the slot. As a further safeguard against fatigue failure it is desirable to eliminate sharp corners along the edges of the slot. As seen in FIGS. 3 and 6, the slot 31 has rounded walls 45 at both its front and rear ends. These rounded walls do not materially restrict the tilting motion of the shaft 11 because the chamfered corners 35 on the drive pin 12 permit the latter to clear the rounded walls 45. These chamfered corners also lessen the danger of fatigue failure of the drive pin 12 because the side faces of the pin are joined at obtuse angles rather than at right angles. The rounded corners 45', as shown in FIGS. 3 and 6, have the shape of a half cylinder arranged in tangential relation to the sides of wall 31. In addition to the advantage of preventing fatigue failure aforesaid, this particular shape has the further advantage that it is convenient to manufacture by drilling holes in the knob to define the end walls of the slot 31.

The axis of the shaft member 11 may be tilted anywhere between the limits of the center lines 32, 33 in FIG. 1 without moving the drive pin 12, retainer pin 42 or trunnion 13 relative to the socket member 16. During such tilting movement, the concave surfaces 38 (FIGS. 1 and 4) on the trunnions 13 engage the spherical surface of the knob along a pair of oppositely facing zones to maintain the center of the knob in alignment with the axis of the socket member 19. The concave surfaces also resist the tendency of the shaft member to move forwardly toward disengaged relation to the socket member.

The axis of the shaft member 11 may be swung horizontally anywhere between the limits of the center lines 46 and 47 of FIG. 3. Upon such swinging movement, the drive pin 12, retainer pins 42 and trunnions 13, swing in unison, thus maintaining the drive pin with its fiat ends engaging the flat sides of the slot 31 in the knob 29. When the shaft 11 is adjusted to the position shown in FIGS. 1 and 3, the impacts transmitted rom the drive pin 12 are directed at right angles to the walls of slot 31, but with a force at the top of the knob applied at a point lying forwardly (closer to the splines 27) than the force which is applied near the bottom of the knob. These two forces combine to transmit torque but, in addition, set up a couple which tends to shift the axis 32 of the shaft member 11 out of registry with the center of the spherical zones 38 on the trunnions 13. This tendency is resisted not only by the trunnions 13 6 but also by the cylindrical counterbore 23 which engages the cylindrical knob 29 about its periphery and thereby inhibits eccentricity between the knob and the trunnions.

If the shaft 11 is swung horizontally to the position indicated by the center line 46 in FIG. 3, the drive pin 12 delivers torsional impulses to the sides of the slot 31 along planes which lie parallel to the line 46. Since the applied force delivered to the pin 12 by the trunnions 13 is in a circumferential direction, and the reactive force from the inclined walls of slot 31 to the pin is oblique, the force of the torsional impulses will be resolved into two components, namely a useful rotary component tending to drive the wrench socket (not shown) and an incidental axial component. Near the upper end of the drive pin 12, the axial component will tend to move the knob 29 in a rearward direction whereas near the lower end of the pin the axial component will tend to move the knob in a forward direction. These two components will combine to set up a tendency to tilt the shaft member 11 about a horizontal axis that passes through the center of curvature of the Zones 38. In accordance with this invention, the operator may resist this tendency (to change the tilting angle of the shaft member 11) by pressing the impact wrench forwardly to cause tight frictional engagement between the spherical surface on the knob 29 and the conical surface on the shoulder 25.

When it is desired to disassemble the universal'joint of this invention, the operator first inserts a hammering pin (not shown) in one of the bores 44 (FIG. 5) at the top of the socket head 21, then hammers through the hammering pin against one end of the retainer pin 44 to drive the latter out of the bore 41, through the loosely surrounding trunnion bore 39 and out through the opposite socket head bore 44. The operator then taps on the upper end of drive pin 12 to remove the drive pin, lower trunnion 13 and lower retainer pin 42 as a unit. The shaft 11 is then free to be pulled out of the socket member 10. If any of the parts of the universal joint are worn, it may be conveniently replaced without necessarily replacing any other part.

While the invention has been illustrated and described with reference to a single embodiment, it may be moditied. For example, the spline drive at each end of the universal joint may be replaced by a square drive. Also, the direction of transmission of torsional impulses may be reversed by connecting the shaft member 11 to the impact wrench and the socket member 10 to the driven nut or bolt. Another modification within the spirit of this invention would involve the transposition of the splined ends 16 and 27 so that the splined opening 15 is provided on the element having an integral knob and the splined shaft end is provided on the element having an integral socket head 21.

What is claimed is:

1. A universal joint comprising a rotatable shaft member having torque transmitting means provided thereon near its front end and having a knob at its rear end, a socket member having torque transmitting means near its rear end and having a central recess at its front end, the knob being mounted within the recess for universal movement relative to the socket member, the knob having a slot extending diametrically therethrough, said slot being defined by flat parallel side walls, a drive pin supported at its outer ends by the front portion of the socket member and extending transversely of the socket member through the slot in the knob, said drive pin having parallel side faces in sliding engagement with the side walls of the slot over a substantial area of contact to impart torque from the socket member through the knob to the shaft member, the drive pin having a cross-sectional area exceeding that of a circle of the diameter of the width of the slot, the slot having sufficient length to permit the shaft member to be tilted about an axis transverse to the pin, a pair of trunnions supporting the end portions of the drive pin and having non-circular openings fitting said end portions, said trunnions being supported for rotation in a pair. of radial bores in the socket member, whereby the shaft member,

the drive pin but which is less than the diameter of the trunnion.

3. A universal joint according to claim 1, in which the socket member has a pair of bores registering with the bores in the driving pin and trunnions to permit the retainer pin to be inserted through one of said pair of bores and driven out of the other of said pair of bores,

4. A universal joint according to claim 3, in which the retainer pin has a tight fit within the drive pin and in which the trunnion bore and socket member bores have a diameter slightly exceeding that of the drive pin bore to facilitate movement of the retainer pin axially through said registering bores during assembly or disassembly.

5. A universal joint according to claim 4, in which the retainer pin is of approximately cylindrical shape being formed by spirally rolling a flat strip of metal under pressure exceeding the elastic limit thereof.

6. A universal joint according to claim 5, in which the retainer pin has a normal diameter when disassembled in excess of the diameter of the transverse bore in the drive pin, whereby the retainer pin is snugly held under compression when assembled,

7. A universal joint according to claim 6, in which the retainer pin is chamfered at one or both of its ends to permit it to be forced into the transverse bore by a series of axial hammer blows.

8. A universal joint comprising a rotatable shaft mem-.

ber having torque transmitting means provided thereon near its frontend and having a. knob at its rear end, ,a socket member having torque transmitting means near its rear end and having a central recess at its front end, the socket member having a shoulder extending rearwardly and inwardly from the rear end of the recess, the knob being at least partly enclosed within the recess and seated at its rear end against said shoulder for universal movement relative to the socket member, the knob having a slot extending diametrically therethrough,

said slot being defined by flat parallel walls, a drive pin supported at its outer ends by the front portion of the socket member and extending transversely of the socket member through the slot in the knob, said drive pin having parallel side faces in sliding engagement with the side walls of the slot over -a substantial area of contact to impart torque from the socket member through the knob to the shaft member, the drive pin having a cross sectional area exceeding that of a circle of the diameter of the width of the slot, the slot having suflicient length to permit the shaft member to be tilted about an axis transverse to the pin, the slot being closed at the rear end of the knob to prevent the shaft member from being detached from the socket member as long as the pin is attached to the socket member, the recess being open at the front end of the socket member to permit the knob to be withdrawn therefrom upon removal of the drive pin in which the drive pin is substantially square in cross section, and in.'which the corners of the pin are chamfered to provide four narrow faces separating four wide faces extending from end to end of the pin.

9. A universal joint according to claim 8, in which the diametrical slot in the knob consists of two oppositely diverging sectors, the ends of the sectors being spaced more closely to the drive pin at the center of the knob than at the peripheral surface of the knob.

10. 'A universal joint according to claim'9, in which each of the ends of the sectors is rounded to form a half-cylinder tangent to the parallel side Walls of the diametrical slot.

'11. A universal joint comprising a driving member having an axial recess in one end, an annular seat defined by a coned wall surface at the back of the recess, and a pair of annular holes through opposite wall areas of the recess; a driven member having a ball-form knob at one end slidably received in the recess, wherein the outer surface of the knob is in tangent contact with the cylindrical wall of the recess and in tangent contact with the coned surface; a bearing element rotatably retained in each of the said holes having a concaved inner surface conforming to the surface of the knob; and means holding the bearing elements in pressed bearing relation upon the knob preventing axial displacement of the knob relative to the annular seat.

References Cited in the file of this patent UNITED STATES PATENTS 526,198 Pringle et al. Sept. 18, 1894 1,225,524 Swartz May 8, 1917 1,522,819 Herbert Jan. 13, 1925 2,121,455 Ten Brock June 21, 1938 2,521,289 Gerst Sept. 5, 1950 2,546,298 Brewing Mar. 27, 1951 2,687,024 George Aug. 24, 1954 

